The invention relates to vulcanizable polymeric compositions containing a zinc dimethacrylate adjuvant and to a method of preparing the adjuvant. More particularly, the invention relates to vulcanizable polymeric compositions comprising certain rubbery polymers or polymer blends, a zinc dimethacrylate adjuvant having specified surface area limitations and peroxide curing agents, and to a method of preparing the zinc dimethacrylate.
Various patents and publications describe the preparation of metallic salts of methacrylic acid.
Thus, Japan Kokai No. 76,138,616 relates to the preparation of zinc dimethacrylate and zinc diacrylate by a process which involves reacting acrylic or methacrylic acid with zinc oxide or zinc hydroxide at 40.degree.-100.degree. C. in water insoluble hydrocarbon solvent mixtures in which the hydrocarbon solvent forms an azeotrope with water, removing the water by azeotropic distillation and drying the resultant product. Hydrocarbon solvents which are disclosed include benzene, toluene, xylenes, cyclohexane, methylcyclohexane, n-heptane, n-hexane, etc.
U.S. Pat. No. 4,082,288 relates to the preparation of basic zinc methacrylate by milling under agitation methacrylic acid with a suspension of zinc oxide in a liquid medium such as water or a volatile organic liquid.
U.S. Pat. No. 4,100,182 relates to a method for preparing an adjuvant for an elastomeric composition which involves mixing methacrylic acid with zinc oxide in a liquid medium in the proportions required to form basic zinc methacrylate, removing the liquid medium and finely dividing the resulting reaction product. The reference teaches that the molar ratios of zinc oxide to methacrylic acid used in forming the reaction product is ordinarily at least 0.8 to 1, preferably 2 to 1 (column 2 lines 18-30); that the liquid medium may be water or a volatile organic liquid such as a hydrocarbon liquid or an alkanol (column 2 lines 45-48) and that the reaction product should be finely powdered to at least a fineness sufficient to pass a 200 mesh sieve preferably a 300 mesh sieve.
U.S. Pat. No. 4,191,671 apparently discloses the in-situ preparation of zinc methacrylate by a process which involves first mixing a rubbery polymer such as polybutadiene with methacrylic acid, then adding zinc oxide thereto in a standard kneader and mixing to obtain a homogeneous rubber composition.
U.S. Pat. No. 4,266,772 discloses the preparation of basic zinc methacrylate using the same process described in U.S. Pat. No. 4,082,288. The article entitled "Elastic Properties and Structures of Polybutadiene Vulcanized With Magnesium Methacrylate" appearing in the Journal of Applied Polymer Science, Vol. 16, pages 505-518 (1972) at page 505 states magnesium methacrylate utilized therein was prepared by heating aqueous solutions of the acid and magnesium hydroxide and then passing the salt through a sieve to obtain salt particles having a diameter of less than 0.5 millimeters.
In addition, various patents and publications describe vulcanizable polymeric compositions containing metallic salts of methacrylic acid.
Thus, U.S. Pat. No. 3,823,122 relates to curable SBR or neoprene elastomer compositions containing from 1 to 15 parts by weight per 100 parts by weight of elastomer of a substituted acrylic acid or acid salt, with the preferred acid salt indicated to be zinc methacrylate which is described as being formed by merely reacting sodium methacrylate with zinc chloride. Elastomer compositions which are disclosed include a reinforcing filler such as carbon black but do not include a peroxide curing agent.
U.S. Pat. No. 4,082,288 discloses free-radial crosslinkable elastomer compositions containing a peroxide crosslinkable elastomer, from 10 to about 60 parts by weight per 100 parts by weight of elastomer of basic zinc methacrylate, a peroxide curing agent and optionally reinforcing fillers such as litharge or zinc oxide in amounts of 2 to 10 parts by weight per 100 parts by weight of elastomer.
U.S. Pat. No. 4,191,671 relates to curable rubber compositions comprising (A) a diene elastomer, (B) an alphabeta ethylenically unsaturated carboxylic acid, wherein the ratio by weight of component (A) to component (B) is 87/13 to 55/45, (C) a divalent metal compound being present in quantities of 50 to 150 parts by weight per 100 parts by weight of component (B), and (D) an organic peroxide being present in quantities of 0.3 to 5.0 parts by weight per 100 parts by weight of the combined weight of components (A) and (B). The compositions may additionally contain an unpolymerizable carboxylic acid, carbon black in amounts of less than 50 parts by weight per 100 parts by weight of elastomer and an amine and/or phenol compound.
U.S. Pat. No. 4,192,790 relates to elastomer compositions having reduced Mooney viscosity in the compounded state. The Mooney viscosity of the elastomer compositions are reduced by the incorporation therein of from 0.1 to 7.0 parts by weight of basic zinc methacrylate per 100 parts by weight of elastomer. In addition to the basic zinc methacrylate, the elastomer compositions contain various elastomers or elastomer blends, an inorganic particulate filler and optionally carbon black (20 to 150 parts per 100 parts elastomer) and curing agents such as peroxide curatives.
U.S. Pat. No. 4,266,772 relates to solid golf balls formed from a curable elastomer composition comprising a freeradical crosslinkable elastomer, especially a peroxide crosslinkable elastomer, basic zinc methacrylate (about 10 to about 60 parts by weight per 100 parts by weight of elastomer) and a curing agent such as a peroxide curing agent. The compositions may optionally contain reinforcing fillers such as litharge or zinc oxide in amounts of for example 2 to 10 parts per 100 parts of elastomer.
British Pat. No. 1,091,818 discloses vulcanizable compositions comprising alpha-olefin polymers and a curing system consisting of metal salts of acrylic acid or methacrylic acid in amounts of from 1 to 10 parts of metal salt per 100 parts of polymer and an organic peroxide. The compositions may additionally contain reinforcing agents and fillers such as carbon blacks, metal oxides, etc.
British Pat. No. 2,042,553 discloses crosslinked cellular elastomeric compositions which are formed from an elastomer composition comprising a natural and/or synthetic rubber, a crosslinking agent such as a peroxide, a monomeric metallic salt such as zinc dimethacrylate, zinc diacrylate, preferably basic zinc methacrylate and a blowing agent. The compositions may additionally contain fillers such as carbon black or titanium dioxide and other known compounding additives.
The article entitled "Vulcanization of Rubbers By Salts of Unsaturated Acids. Vulcanization of Butadiene-Styrene Rubber By Methacrylate Salts" by A. A. Dontsov et al. appearing in the Colloid Journal USSR, Volume 31, pages 293-297 (1969) discloses vulcanizable compositions comprising butadiene-styrene rubber or ethylene-propylene rubber, magnesium methacrylate or sodium methacrylate and dicumyl peroxide.
The article entitled "Elastic Properties and Structure of Polybutadiene Vulcanized with Magnesium Methacrylate" by A. Dontsov et al. appearing in the Journal of Applied Polymer Science, Volume 16, pages 505-518 (1972) discloses vulcanizable compositions comprising polybutadiene, magnesium methacrylate and dicumyl peroxide.
The article entitled "General Regularities of Heterogeneous Vulcanization" by A. A. Dontsov appearing in the publication Rubbercon '77, International Rubber Conference, Volume 2, pages 26-1 through 26-12 (1977) discloses vulcanizable compositions comprising styrene-butadiene rubber or ethylene-propylene rubber; magnesium, sodium, zinc and cadmium salts of methacrylic, maleic and betaphenyl acrylic acids and radical type initiators such as dicumyl peroxide.